Interrelated studies are now being carried out to establish how unsaturated fatty acid metabolism is altered in the streptozotocin induced diabetic rat and whether these alterations influence platelet aggregation thus contributing to the more rapid onset of vascular disease in the diabetic. To date our studies have focused primarily on the microsomal chain elongation system. The rate of this process is influenced by dietary change. Our results also suggest that microsomal chain elongation probably is carried out by discrete enzymes rather than a single multifunctional complex. Studies now in progress are designed to determine how dietary variation in conjunction with experimental diabetes influences both the rate of desaturation and chain elongation of unsaturated fatty acids.